1. Field of the Disclosure
The disclosure relates generally to image scanning devices, and, more particularly, to a scan bar used for scanning a media sheet in an image scanning device.
2. Description of the Related Art
Image scanning devices, such as scanners, are typically used for scanning information provided on media sheets such as papers, transparencies, picture negatives and the like. Scanning the information provided on a media sheet refers to converting the information provided on the media sheet into a digital image. The digital image may then be viewed on a screen of a data processing device such as a personal computer, a laptop, a personal digital assistant and the like.
The image scanning devices, typically, include a platen and a scan bar for scanning the media sheets. The media sheet is placed on the platen such that a side of the media sheet including the information to be scanned faces the platen. The scan bar is positioned adjacent to the platen and typically includes a light source, a lens and a sensor module. The light source illuminates a portion of the media sheet and the light reflected from the portion of the media sheet impinges on the lens. The lens may be configured to focus the light onto the sensor module. The light focused by the lens onto the sensor module includes an optical image of the information included in the portion of the media sheet. The sensor module converts the received focused light, i.e. the optical image, into a digital image, thereby scanning the information included in the portion of the media sheet. The media sheet or the scan bar may be moved relative to each other for scanning all of the information on the media sheet.
Scan bars of the image scanning devices are typically available in one of a high resolution scan mode, such as 4800 pixels per inch (ppi), or, a low resolution scan mode such as 1200 ppi, 600 ppi, 300 ppi and 200 ppi. Scanning the media sheet at the high resolution scan mode provides higher quality scans, i.e., better digital image quality and improved clarity, whereas, scanning the media sheet at the low resolution scan mode provides relatively poorer scan quality than scanning at the high resolution scan mode. Potential customers of the image scanning devices typically prefer an image scanning device configured with a scan bar capable of scanning at the high resolution scan mode.
Scanning of media sheets, such as an 8.5 inches×11 inches document or a 4 inches×6 inches document using a scan bar at high resolution scan mode, such as 4800 ppi, may result in several gigabytes of file size of the digital image. Such a large file size of the digital image of the document may render the high resolution scan mode of the scan bar, in the image scanning device, to be usable only for limited applications.
Moreover, most scanning operations, i.e. scanning of the media sheets, are performed at default settings of the image scanning devices. The default settings of the image scanning devices are typically set at low resolutions such as 200 or 300 ppi. Scanning of the media sheets by scan bars capable of scanning at the high resolution scan mode, such as 4800 ppi, at default settings have revealed a degradation of image quality of the digital images captured by the image scanning devices. Such degradation of the image quality may be due to smaller sensors configured in a sensor module of the scan bar. Further, the degradation of image quality may be due to limitations of lenses present in the scan bar of the image scanning device that result in increased signal noises, reduced dynamic range and lower spatial frequency response.
Based on the foregoing, there is a need for a scan bar in an improved image scanning device.